Recording material and method for the production of the same

Abstract

The recording material comprises a base sheet and a color former coating layer formed on a surface of the base sheet and the color former coating layer is formed by coating a surface of the base sheet with a coating composition comprising an aqueous dispersion of microcapsules each encapsulating a hydrophobic color former material therein and having a capsule wall of a gelated hydrophilic colloid material. The dispersion further includes (a) a hardener for the hydrophilic colloid material and (b) a water soluble alkali salt of a copolymer of at least one olefinic monocarboxylic acid with at least one monomer copolymerizable with the olefinic monocarboxylic acid.

What we claim is: 
     
       1. In the method for the production of a recording material comprising a base sheet and a color former coating layer formed on a surface of said base sheet, said color former coating layer including microcapsules each encapsulating a hydrophobic color former material therein, an improvement in the steps of (1) preparing an aqueous dispersion of said microcapsules each having a capsule wall of a gelated hydrophilic colloid material and containing a hydrophobic color former material therein,   (2) adding to said dispersion at least one hardener for said hydrophilic colloid material selected from the group consisting of aldehydes, diketones, epoxides, acid anhydrides and acid chlorides,   (3) hardening said capsule walls of said microcapsules with said hardener,   (4) adding to said dispersion a water soluble alkali salt of a copolymer of 8 to 90 mol % of at least one olefinic monocarboxylic acid with 92 to 10 mol % of at least one monomer copolymerizable with said olefinic monocarboxylic acid, said water soluble alkali salt of a copolymer having a surface tension of at least 40 dyne/cm in a 1 weight % aqueous solution and the amount of said water soluble alkali salt of a copolymer included in said dispersion being within the range of 0.5 to 50 parts by weight with respect to 100 parts by weight of said hydrophobic material of said microcapsules, and   (5) coating a surface of said base sheet with said coating composition to form said color former layer.   
     
     
       2. A method for the production of a recording material according to claim 1, in which said olefinic monocarboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid and crotonic acid. 
     
     
       3. A method for the production of a recording material according to claim 1, in which said copolymerizable monomer is an acrylic monomer or methacrylic monomer. 
     
     
       4. A method for the production of a recording material according to claim 3, in which said acrylic monomer or methacrylic monomer is selected from the group consisting of alkyl acrylates having an alkyl group having 18 or less carbon atoms, alkyl methacrylate having an alkyl group having 18 or less carbon atoms, acrylonitrile, methacrylonitrile, acrylamide and methacrylamide. 
     
     
       5. A method for the production of a recording material according to claim 3, in which said hydrophilic colloid material is gelatin. 
     
     
       6. A method for the production of a recording material according to claim 1, in which said water soluble alkali salt of copolymer has a surface tension of 45 to 72 dyne/cm in a 1 weight % aqueous solution. 
     
     
       7. A recording material comprising a base sheet and a color former coating layer formed on a surface of said base sheet said color former coating layer including microcapsules each encapsulating a hydrophobic color former material therein, said recording material produced by the steps of: a. preparing an aqueous dispersion of said microcapsules each having a capsule wall of a gelated hydrophilic colloid material and containing a hydrophobic color former material therein;   b. adding to said dispersion at least one hardener for said hydrophillic colloid material selected from the group consisting of aldehydes, diketones, epoxides, acid anhydrides and acid chlorides;   c. hardening said capsule walls of said microcapsules with said hardener;   d. adding to said dispersion a water soluble alkali-salt of a copolymer of 8 to 90 mol percent of at least one olefinic monocarboxylic acid with 92 to 10 mol percent of at least one monomer copolymerizable with said olefinic monocarboxylic acid to form a coating composition, said water soluble alkali salt of a copolymer having a surface tension of at least 40 dyne/cm in a 1 weight percent aqueous solution, the amount of said water soluble alkali salt of a copolymer included in said dispersion being within the range of 0.5 to 50 parts by weight with respect to 100 parts by weight of said hydrophobic material of said microcapsules; and   e. coating a surface of said base sheet with said coating composition to form said color former layer.   
     
     
       8. A recording material according to claim 7, in which said olefinic monocarboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid and crotonic acid. 
     
     
       9. A recording material according to claim 7, in which said copolymerizable monomer is an acrylic monomer or methacrylic monomer. 
     
     
       10. A recording material according to claim 9, in which said acrylic monomer or methacrylic monomer is selected from the group consisting of alkyl acrylates having an alkyl group having 18 or less carbon atoms, alkyl methacrylate having an alkyl group having 18 or less carbon atoms, acrylonitrile, methacrylonitrile, acrylamide and methacrylamide. 
     
     
       11. A recording material according to claim 7, in which said hydrophilic colloid material is gelatin. 
     
     
       12. A recording material according to claim 7, in which said water soluble alkali salt of a copolymer has a surface tension of 45 to 72 dyne/cm in a 1 weight % aqueous solution.